Comparing the effects of different coloured artificial illumination on diurnal fish assemblages in the lower mesophotic zone
Artificial illumination is required when sampling with baited remote underwater video systems (BRUVS) in the lower mesophotic zone beyond ~ 90 m depth, yet little is known of how the choice of lighting influences fish assemblages and affects survey results in this zone. Here we use BRUVS equipped with the commonly used GoPro action camera to compare the composition and abundance of diurnal fish assemblages sampled under artificial Royal blue (~ 450 nm), Deep red (~ 660 nm) and natural day white light (~ 5600 K) in the lower mesophotic zone of the north-west shelf of Australia (19° 14.724′S 117° 20.286′E). No significant differences were detected in the fish assemblage composition or the number of species when surveyed using blue, red or white light at our study location. A greater mean total abundance of fish was observed using red light compared with white and blue light, however, individual species showed varied responses to the different light colours. When using consumer-grade action cameras such as GoPros, white light was shown to be far superior in image quality (and therefore ease of fish identification) compared to red and blue light. We recommend sampling diurnal mesophotic fish assemblages using a wavelength of light based on the survey objectives and the capabilities of the camera selected.
This study was part of the Seabed Biodiversity and Habitats Research Theme within the North West Shoals to Shore Research Program, a collaboration between the Australian Institute of Marine Science and Santos (https://www.aims.gov.au/nw-shoals-to-shore/seabed-habitats-and-biodiversity). We would like to thank the master and crew of the RV Solander along with all other field support personnel. We would like to thank the two reviewers for their constructive revisions which improved this manuscript.
This study was funded by Santos and the Australian Institute of Marine Science.
Compliance with ethical standards
Conflict of interest
Matthew Birt declares that he has no conflict of interest. Marcus Stowar declares that he has no conflict of interest. Leanne Currey-Randall declares that she has no conflict of interest. Dianne McLean declares that she has no conflict of interest. Karen Miller declares that she has no conflict of interest.
All applicable international, national and/or institutional guidelines for sampling, care and experimental use of organisms for the study have been followed.
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